## Uncertainty Principles

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"Where are we going?"

"You'll see."

"Where are we going?" he demands again, but the problem with a circular console is the same problem that arises when you try to play tag around a circular table. He tries to catch a glimpse of the destination screen and the Doctor pulls on some lever that the Master could have sworn was the thermostat, yesterday, and suddenly the screen goes blank.

He grabs hold of a lever of his own, not at all above blackmail, and looks up. "Doctor, you should have told me that we were allowed to start pulling pigtails. I'd have plaited my hair especially for the occasion."

"Don't be absurd," the Doctor says, with an absurd smile on his face. "Why does it matter where we're going?"

"Oh, well," the Master shoots back waspishly. "I need to know if I should bring my parasol, or if I should be expecting a civil war. Is this some new petty game of dominance you've decided to play? It's hardly original, if so."

"Don’t pull that." The Doctor eyes his hand.

He smiles and puts the palm of his other hand against a row of buttons; he knows what these ones do, he's worked most of it out by now -- honestly, does the Doctor think he's stupid? -- but he also knows how to act like he doesn't. "I may not be able to steer a course but I can certainly throw off yours, and I think I'll start pulling on whatever I like until you, Doctor, give me an answer: where are we going?"

"Everywhere!" the Doctor shouts, loud and abrupt, his voice ringing in the high corners of the control room. Then he laughs. "We're going everywhere! If you don't look at the screen then you don’t know, and if you don't know then you have no expectations, which means --" he pulls a hand away from the controls and points at the door "-- until that door opens, we could be anywhere and anywhen, and so in a way we are everywhere at once."

The Master stares at him in horror. "Schrödinger's fucking time machine," he says. "Let me off. You're almost starting to make sense."

mechanics part i (classical)

"What do you think?"

Koschei leans his chin on Theta's shoulder and peers down at the calculations.

"Of course it does, it's from a textbook." Theta jabs at his workpad and frowns. "All this accuracy is boring."

Koschei goes back to what he was doing, which was drawing an intricate kind of ambigram on the back of Theta's free hand. There are words that mean the same thing when looked at from opposite sides; he is attempting to work a sly antonym into the script, so that the meaning will change depending on the angle of the viewer. Or of the hand. He is fascinated by Theta's hands, by the possibilities created by each vehement flick of the the pale fingertips, and the promising creases of the palms. Lifelines that whorl around each other and never end.

"What do you mean, boring?" he asks, vague, distracted by the skill of his own brush and the way the other boy's joints lock in a shiver of appreciation whenever he presses down hard.

"The universe isn't predictable. I wish they'd stop teaching us about the equations and show us the parts that can't be quantified."

He frowns and looks back at the screen. "These parts seem important."

"My head hurts." Theta pushes the pad away. "Let's do something else."

Koschei smiles and puts his brush down; lifts the hand and blows gently across the ink, watching the wet sheen fade into a black that sucks in the light instead of reflecting it, and when he looks up it's to find Theta's eyes gone amused and almost as dark.

"Think about it," Koschei says then. "We're learning the laws of the universe; if we learn them all then surely that gives us a kind of mastery? Something as vast as a galaxy and you can predict exactly the right amount of force required to move it exactly as you desire."

"You can't move a galaxy," Theta says.

Koschei laughs. "But the point is that you know how. In theory. It's just a matter of finding a way to apply it."

Theta tilts his head in consideration and then leans forward until their breaths are mingling with humour and heat; he lifts up the back of his hand, upon which is inked a word that flickers between leave and stay, and he whispers, "For every action there is an equal and opposite --"

And the Master wakes up with his breath raw in his throat and the drums screaming against his skull.

nodes & anti-nodes

"A lake." The Doctor's nonplussed expression is fantastic. "I let you pick the destination and you take us to an Earth lake?"

The Master laughs and leans out of the doorway, letting the shield catch him. "Saltstraumen, Doctor! The strongest tidal current on the planet -- and, incidentally, this arm of the galaxy. Strange, the things this little mudball turns up, if you know where to look. And it's not a lake, you know." He tuts with his tongue and tastes salt. "It's a sound."

"Norway," the Doctor says, and he sounds strange.

"What of it? Did you want to go fishing? Come on, I've led us to the water and now you have to drink. So to speak." He gives the Doctor a push towards the console. "Unless you'd like to let me drive, dear, but you know how I always have to stop and ask for directions."

The Doctor's hands are on the controls and he gives the Master a look that's more suspicious than anything else, like he thinks the Master might have sabotaged something. The Master smirks and turns back to the door, and after a long pause the TARDIS shudders into life and they land on the first blunt wave with a stomach-swooping splash.

Saltstraumen is a microcosm of patterns within chaos, long deep tugs and whirlpools that kick up paper-thin walls of white spray. The Master steadies his feet against the floor and watches the water hit the shield, feeling precarious and young, and when they surge upwards to meet a twist of tide he glances backwards. The Doctor is giving him that suspicious look again.

He rolls his eyes. "Obviously, the thrill of our imminent death. Oh, no, I forgot: it's you that has the death wish --"

"Is that what you think?" the Doctor snaps.

"Prove me wrong!"

"Stop that."

The Master takes five angry strides forward and in a dead language of which they are the sole pallbearers he whispers: prove it. In a society of mathematicians the highest manner of formal speech is required for any invitation to complete a proof, but the Master elongates the last vowel and so slides an insult into it as well: Prove it; I don't think you can.

The Doctor slams his hand down onto a panel and the TARDIS jerks to a stop. Waves slap violently against the exterior, protesting this new obstacle in the way of their momentum, and the Doctor looks as furious as the Master can remember him being.

"You think you understand me so well? As if I would leave you, you, alone in the universe, as if --"

"As if what?" the Master whispers, fury shaving his words into fine slivers of sound, but the Doctor is staring at him and he realises that both of them might have heard that last sentence entirely wrong.

The Doctor's face goes through at least four different emotions and ends up, for a very brief moment, on a kind of naked fear. Then -- "You drive," he says in a voice that's dark and ductile like burnt spun sugar, and walks over to the door. "You don't need formal access to steer around a lake." He catches the frame with his hands and leans out just as the Master had before, rising onto the toes of his ridiculous sneakers.

The Master gazes at his back for a moment and then steers them into the biggest whirlpool he can find. It probably won't kill them, but if he hits the water at the right angle then maybe it'll be enough to knock the Doctor right off his feet.

solenoid

Stretched out below them the Night Market of Galaad'skx is a flood of lights in different shades of blue. The economy is basic, agrarian -- the Master could probably triple the planet's universal progress classification in less than a year if he imported a bit of silicon and nudged their scientists in an interesting direction -- but from this height the scene is as bright and neon-rich as any cityscape.

The Doctor looks restless. "Are we done here?"

"No." He turns around and leans his bare elbows on the rail and watches the dip of the Doctor's throat in the undone triangle of his shirt. The air is warm and dense. "Are you in a hurry to leave?"

"No! No, I thought we would, you know. Go down there. Actually talk to people," the Doctor says, reproving, and the Master scoffs silently as he turns to stare at the vast carpet of activity once more.

"Ah, because that's your thing, isn't it? The personal touch. Very sweet. Come now, Doctor, you need to find some variety of perspective."

The Doctor sighs and joins him at the rail. The wind is intermittent but strong, kicking dust up at their feet, and the tiny lights form meaningless patterns that spin across their retinas. "All right. The view is fantastic. Very..."

"Chaotic."

"Yes." The Doctor frowns. "I don't think I like who I turn into around you, sometimes."

"I know," he replies. "Because that person is more real."

"That's not true." Steady. "That's not why this is difficult." His hand waves on this, a vague gesture that would mean nothing to anyone who hadn't grown up with an intimate knowledge of that hand's subtle tells, the language that remained constant beneath the quirks of regeneration. To the Master that gesture encompasses the both of them, the planet, the TARDIS, the stars above their head -- the circumstance that has their personal timelines curving in parallel for the time being and perhaps for a long time to come.

"No. It's difficult because you feel responsible for me, and my God, Doctor! How you hate being the sane one. How you hate being the responsible adult." He grins, fluid and exultant with how good this feels. "Spending your time dragging humans around with you so that you can be the overgrown child with your sense of wonder spilling into their more rational minds. So you've got someone to grab onto your shirt before you topple yourself over the edge of the waterfall, trying to catch a glimpse of the bottom."

The Doctor has a look in his eyes like he's somewhere years and light years away, watching something die in its sleep. He gets that look a lot; the Master would be quite happy to never see it again as long as they both live, because it makes him feel judged and angry and alone.

He steps closer. "I'm not going to stop you from jumping. Not ever."

More of that far-off melancholy, and then the Doctor gives a sudden smile that brings him hurtling back into the present moment at something like the speed of light.

"'Course not," he says, with his familiar near-manic cheerfulness. "You're going to jump too, because you can't stand the idea that there might be something interesting at the bottom, and I might find it first."

specular reflection

The TARDIS makes sounds even when she isn't moving, even when they're parked on a dusty moon in some corner of the universe with nothing to recommend it but the vast sepia panorama streching away from the doorway and, apparently, a rift just big enough to use for fuel. The Doctor is off in a room somewhere trying to make his greenhouse stop disappearing into the fifteenth century and the Master is standing with his hands resting on the console, listening to the TARDIS. He's learned more of the levers now, even the ones that change their function depending on whether they're heading for the future or the past, or whether or not the wormhole synthesiser is engaged.

There's a low thrum that sounds almost ominous, and he lifts his hands away with a laugh; considering what he created the last time he laid hands on the TARDIS, he doesn't begrudge her the wariness. "All right," he murmurs. "Point taken."

The metal bears scars and dents and stains, and sometimes a flicker of crimson red snakes up the edge of a light source. The Master finds brilliantly intricate circuitry held together with bent wire clips and the artful use of tape, and half a dozen scraps of paper adorned with near-illegible Gallifreyan shorthand for a personal timeline: a halfhearted shadow of a ship's log. And engraved on the lower edge of an unremarkable panel, two Greek letters; one of them looks almost like an egg bisected horizontally by a needle, and when taken together they mean the sum of the angles. The Master isn't quite comfortable with the fact that he knows this, or that his mind should slip so easily into the quantitative systems of a different race.

He lifts one hand and runs the tip of his finger within the symbols, picking up dust, marvelling at the fact that the Doctor should have kept part of his own identity in plain sight while refusing to speak it aloud. That he should want to remember this part of him, this boy who threw himself through the vacuum of space and time and no matter what struck him, he survived; he just bounced right off again and carried on, bruised and disoriented, adrift in his own momentum.

Although on reflection it does seem like a very Doctor thing to do, to live with this reminder of the past staring him in the face, like a painful signal set at a wavelength that only he can hear.

"You selfish, masochistic bastard," the Master says, before he remembers that there's nobody to hear him.

The drums are loud today.

specific heat

It could be the fact that running away is a lot more enjoyable than he'd thought it could be, and it could be the fact that the Doctor didn't seem to think before reaching out and grabbing the Master's hand in his own, but in all honesty the Master can't really put his finger on the reason why he begins to gather in his mind a thin bolt of personal energy, mocking laughter wound around a centre of desire and drawn tight by the way an ink-wet brush feels as it drags across your wrist.

They dash around a corner, leap over a puddle, and just as his feet hit the ground again the Master sends the energy straight down his arm, across the synapse of skin, and into the Doctor's mind.

The Doctor drops his hand like it’s on fire, screeches to a halt and looks at him: startled, the Master judges, but not shocked.

"Don't," he says, clearly jittery in his eagerness to start running again. "This is hardly the time." He makes a grab for the Master's hand again -- appears to think better of it -- and stops halfway there, looking wary.

"My mistake," the Master says solemnly.

"Fine! Stay and be captured." The Doctor starts walking backwards. "That should be adequate entertainment even for you."

"I do hope so." The Master pulls the sonic screwdriver from his pocket; he lifted it over an hour ago, and has been waiting for the Doctor to notice, but this is a lot more fun. "I might be able to offer them some weapon upgrades; that ought to spice up the gang wars, don't you think?"

"You --" The Doctor makes a useless go of patting down his own pockets. Around the corner, behind them, the sound of running footsteps starts to crescendo.

He tosses the screwdriver once or twice and then puts it back in his pocket and holds out his hand. The Doctor looks furious, and like he's bracing himself for something, but he grabs the Master's hand again.

The Master smiles widely and does nothing at all.

The Doctor says something under his breath that's neither audible nor, the Master suspects, polite, and then they're running again. Just to keep things interesting, the Master sends him little jolts of sensation at random intervals, but the Doctor doesn't react beyond brief spasms of the muscles in his arm, and the Master keeps everything light and teasing right up until the moment the door of the TARDIS swings all the way shut, and then he throws his mind open and begins to laugh.

The Doctor makes a strangled sound and falls to his knees, which is...gratifying, but not as much as the Master had thought it might be. He keeps laughing -- can't stop, the sensation is too wide and too bright, like fireworks and rebirth and sparkling water -- and leans down, bracing his arm to pull the Doctor back onto his feet, but then something fast and violent happens and suddenly he's sprawled awkwardly on the ground and the Doctor is propped up on one elbow staring at a tear in the Master's shirt.

The Master moves his head, winces at the throbbing echo that remains after the sudden slam of the Doctor's shields against his wide-open stream of chaos, and then raises his eyebrows. "Well --"

"You're absolutely rubbish," and the Doctor swallows audibly and moves his gaze, defiant, from the Master's shirt to his face, "at finishing the things you start. Taking responsibility for them. You're useless. So finish." But his voice breaks on the last word and then he says, "Please," and puts his fingers against the Master's temples and kisses him.

The Doctor's mind is a rainstorm, a deluge of broken pieces and inexorability, falling into the cracks. The Master wrestles to keep his own identity intact and remembers, wonders how he'd ever managed to forget, the glorious breadth of this feeling, of drowning in someone else's thoughts. Golden circles of life and death that blur the present in both directions -- the Doctor kissed him and now they are breathless and struggling with buttons on the sloped floor of the TARDIS and maybe the Master is painting upside-down patterns onto the Doctor's palms with his mouth or maybe that hasn't happened yet, and the storm is accelerating around them, faster and faster, but maybe they're too old for subtlety and maybe they're too young. Now is --

The Master finds himself in the Doctor's mind and anchors them both, and time spills out blind in every direction.

ohm's law

The problem is that even when he entertains the illusion of choice, by staying he is constantly resisting his own nature, and he channels that resistance and then flings it out onto the Doctor. They are closer to where they began. They are the two arms of a galaxy spinning wide across space, equal and opposite, and he has always hated stasis and the Doctor has always hated keeping prisoners.

The Master looks at the door, which is closed, but which might -- might -- open if he pushed it carefully and asked it to.

"Yes. You could give me the freedom to leave. What do you imagine would happen?"

"Well," the Doctor says, dragging the word out in that way that he has, the one that makes the Master want to kick him. "You'd probably go off somewhere and make some grand destructive gesture to get my attention, and I'd come running, and you wouldn't kill me because then your life would be too boring and I wouldn't kill you because --"

The Master shuffles through lives and memories and heat slides down his spine. "Because," he says, and he thought he was turning it into a question but it comes out sounding more like an answer.

"Right," the Doctor says unevenly. "Because. So really, the whole thing would be a lot simpler if you could just learn to work on the assumption that you have my attention. All of it."

Silence. The TARDIS makes one of her strange settling noises and he knows better than to take it as an invitation, but at least it no longer sounds like a threat.

"Simpler," the Master says.

The Doctor looks at him and sighs. "I know, I know." He sounds tired. "Bad choice of words there. As if anything could ever be simple with you. But -- stay. Please."

He says, "You can't expect," and stops. He says, "You can't make them go away just by -- by understanding me. A call to war. Always."

"War?"

Something about the sharpness of the Doctor's voice means that he actually thinks about it; actually calls up the drums and lets them thud louder into the silence, and discovers to his surprise that something was lost in translation. Within the syncopy the word is war but only because no human word can express the superlative of a verb.

So what he says then is something that sort of means fight but is bracketed with a grammatical structure that means the imbuement of a life. Fighting as a purpose, an unalterable point in history, shards of destiny spat out from the Vortex and buried deep in his child's eyes and his terrifed hearts.

The Doctor doesn't smile, but there's an old mischief alight in his face. "I see," he says. "And do they ever specify what, in particular, they need you to fight against?"

mechanics part ii (quantum)

"All I'm saying is that the focus on physicality is -- crude. Underevolved. Fun enough as a scaffold, but, well, it's just not interesting, is it? Without the --" Tapping his fingers against his temple, because yet again there's no word for it in any tongue but their own, and he isn't quite ready to construct any phrases about sex in a language that makes it impossible to do so without defining very precisely the parameters of emotion and possession within which the act will take place. The suffixes are so exact that they're almost a legal statement; almost a declaration. A promise.

A hand touches his cheek and it has no temperature at all, not cool and not warm, like water that has reached equilibrium with the room around it and is thus imperceptible until your fingers are almost submerged. The Doctor's hand has no temperature as it moves to cover his eyes, and the science of that is that they are exactly the same.

"Really?" the Doctor says, very quietly. "Oh, I'd credited you with a little more imagination than that."

He smiles in the gentle pressure of the darkness. "That sounds like something I’d --"

Say, but he doesn't, because in that moment the Doctor's mouth is beneath the angle of his jaw, pressed above the pulse. Just for a second.

He shivers. He could step backwards at any time. He might wait a little longer.

Next is two fingers -- these ones warm -- against the inside of his elbow and then gliding up under the cuff of his shirt, which has been carelessly folded back and folded back and folded back again.

Eyelashes, against his cheek, and he wants to laugh at the childishness of it but he's busy trying not to show just how impressed he is with the fact that the Doctor was right. When the contact could come from anywhere and their minds are isolated and can provide no clues, the anticipation of touch crawling across every inch of his skin is like the Doctor has managed to paint him in a pastel shade of tactile sensation. All right. It's -- interesting.

"Here next," he commands, as an experiment, and lifts the back of his left hand. He is now almost certain that if he pushed the door of the TARDIS, it would open.

He might wait a little longer.

A tickling soundless laugh traces its way across his face and then withdraws.

The Master exhales, and waits, and thinks about how not being touched at all is remarkably like being touched everywhere at once.

q.e.d.

They are arriving at the future through a series of systematic retreats. Working backwards from an unknown and unalterable point in time to discover why the fabric of existence needs them to arrive there; why a lever inserted into now and not then can be pushed down upon to move the universe and create -- them. They are fighting boredom, fighting the wars that they stumble across, fighting the laws of the universe and fighting each other. The drums never waver, but their tone falls from the imperative into the steady; a rhythm to live one's life by.

He can fly the TARDIS in three dimensions, but she still won't give him the fourth.

And there is nothing really static about perpetual tourism, especially given the Doctor's knack for embroiling himself in the most violent aspects of a foreign culture; unspoken but unshaken is the Master's knowledge that the purpose that the Vortex gave the Doctor was running, and so together they are an instant revolution: just add heat.

"I think you might have broken at least ten laws," the Doctor hisses.

The Master takes another of the small pink not-quite-mints from the bowl on the table and puts it in his mouth. "Good, these. Don't be such a hypocrite, you've broken more local laws than you've had cups of tea."

"You --"

"Stole an unrefined probability filter," he supplies. "It's wasted on these people, they were using it for decoration. They probably thought the density function was nothing more than pretty twinkling lights."

The Doctor looks away, not quite fast enough to hide the twitch of his mouth. "One day you're going to cross the line."

The Master, for whom all lines of that kind have always been invisible and incomprehensible, is curious about that day. He knows the direction in which the line lies, but not the distance he will have to go to reach it, and dancing on half a vector has always been his preferred way of living.

So for now he shifts his weight from foot to foot and watches, with restless delight, as the hushed conversation taking place in front of them begins to turn sour. A guard holding something long and pointy lowers its head and its weapon in their direction, clearly about to say something along the lines of you're coming with me. He's beginning to get a feel for how this goes.

"You stole the bloody thing. It's your turn to come up with an idea," the Doctor mutters.

Every time he doesn't leave, every time he makes a choice, he feels the universe splintering under his hands. Their threads are unwinding in the fabric of time and space, tangled and true, mapping a single unpredictable path between the multitude of great unknowns.

"Live to fight another day," he says.

"Right," and the Doctor slides his hand into the Master's in a single smooth movement, throws him a wild grin, and tightens his grip. "Run!"